1. Field of the Invention
The present invention relates to the field of formation fluid sampling and analysis and in particular to the field of reservoir characterization using photoacoustic spectroscopy.
2. Background Information
To obtain hydrocarbons such as oil and gas, boreholes are drilled into the earth by rotating a drill bit attached to the end of a drill string. Modern directional drilling systems generally employ a drill string having a bottom hole assembly (BHA) and a drill bit at an end thereof that is rotated by a drill motor (mud motor) and/or by rotating the drill string. A number of downhole devices placed in close proximity to the drill bit measure certain downhole operating parameters associated with the drill string. Such devices typically include sensors for measuring downhole temperature and pressure, azimuth and inclination measuring devices and a resistivity-measuring device to determine the presence of hydrocarbons and water. Additional downhole instruments, known as logging-while-drilling (LWD) tools or measurement-while-drilling (MWD) tools, are attached to the drill string to determine the formation geology formation fluid characteristics and conditions during the drilling operations. Wireline logging tools are typically used after the drilling of the wellbore to determine formation geology and formation fluid characteristics.
Commercial development of hydrocarbon fields requires significant amounts of capital. Before field development begins, operators desire to have as much data as possible regarding the nature of the hydrocarbon formation in order to evaluate the reservoir for commercial viability. Despite the advances in data acquisition during drilling using the MWD tools and the analysis done by wireline tools after drilling the well, it is often necessary to analyze formation fluid from different wells at different locations in the reservoir. These samples are compared to estimate reservoir compartmentalization of the reservoir.
The degree of reservoir compartmentalization is important because it aids oil producers to decide on how to develop a reservoir (well location, types of production facilities, etc.). Oil producers want to know whether different sections of a reservoir are separate compartments (across which fluids do not flow) or whether they are connected. Separate compartments are drained separately and may need different types of processing for their fluids. Thus, there is a need for methods and apparatus for determining whether or not a reservoir is compartmentalized.